The present invention relates in general to devices which warn when a fluid level drops below a predetermined limit, and in particular to a new and useful device which uses a separate levelness sensor to trigger an alarm when the fluid level in a container drops below a predetermined limit. A novel type of mercury switch, useful in connection with the invention is disclosed.
The invention described and claimed herein comprises a levelness sensor (for example, a mercury switch) encapsulated in a conically shaped inert material (such as TEFLON.TM.), sized appropriately to the predetermined fluid limit, and coupled to an alarm device (such as an audible alarm, a radio frequency signal or a light emitting diode).
There are many situations in which undesirable results will follow if a given fluid level drops below some critical point. For example, in column chromatography, a solvent flows through a column and various chemicals and biochemicals are separated. The solvent is applied to the column by means of a pump or hydrostatic pressure to maintain a steady solvent flow through the system. If the containers with the solvent run empty then the column runs dry, which can destroy the column and the separation process. In the home, if a container of liquid is left on a stove to boil and boils dry, the container may be destroyed and may cause a fire. More generally, the status (empty or not) of an opaque container, for example a coffee carafe, can be determined, and can even be monitored remotely.
Inclinometers are well-known in the art. See, for example, U.S. Pat. No. 4,912,662 (INCLINOMETER) issued Mar. 27, 1990 to Butler et al., which is incorporated herein by reference. The special aspect of a mercury switch, that it is triggered by the flow of liquid mercury which by nature will remain level, has previously been used as a levelness sensing device in the broad sense. U. S. Pat. No. 2,692,652 (SAFETY DEVICE FOR USE WITH TRACTORS AND THE LIKE) issued Oct. 26, 1954 to Wilson couples such a switch to the power system of a tractor so as to stop the engine when a tractor travelling over uneven ground tilts to an unsafe level. The Wilson patent describes the operation of a mercury switch, and is incorporated herein by reference. The invention disclosed herein, however, couples the inherent level-sensing property of the mercury switch with a shape deliberately designed to tilt out of level when the fluid in which it floats no longer supports it.
Among the objects of the present invention are to provide a new and useful apparatus which warns when a fluid level drops below a predetermined limit and which has the additional advantages of being able to transmit the alarm to a remote location; of using very little energy except when in an alarm mode and thereby being suitable for encapsulation with a power source such as a lithium battery and thus requiring no external power cables; of being capable of manufacture in a small package suitable for use in small containers; of being self-contained and therefore washable and autoclaveable; of being suitable for manufacture of an inert material and therefore being suited to use in sterile or corrosive environments; and of being able to accommodate additional sensor and signalling devices in the same package.
These and other objects, advantages and features of the invention which will be apparent from the discussion which follows are achieved, in accordance with the invention, by providing a levelness sensor (for example, a mercury switch) encapsulated in a conically shaped inert material (such as TEFLON.TM.), sized appropriately to the predetermined fluid limit, and coupled to an alarm device (such as an audible alarm, a radio frequency signal or a light emitting diode). While any levelness sensor may be used, the description which follows will use the example of a mercury switch as the levelness sensor.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its advantages and objects, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.